1. Field of Invention
This invention relates to motor vehicle parts and accessories and particularly to dipsticks useful in the engine lubricant (oil) reservoir (at times referred to as “oil pan” of the engine for a motor vehicle.
2. Background
In motor vehicles, dipsticks are employed for purposes of visual inspection of the quantity (and to a lesser degree of the quality) of fluid located within a closed reservoir in a motor vehicle. In general, oil reservoirs of motor vehicles commonly are provided with an opening leading from external of the oil reservoir into the interior of the reservoir. Often this opening is provided with a fitting, such as a hollow tube. An inboard end of the tube is mounted in the opening leading into the reservoir with the tube extending from the oil reservoir to a terminal location within the engine compartment of the vehicle where the outboard end of the tube is commonly anchored to an engine head or other structure within the engine compartment of the motor vehicle, remote from the oil reservoir. Thus, the open outboard end of the tube is readily accessible within the engine compartment of a motor vehicle. An elongated removable dipstick commonly is inserted into the outboard end of the tube and extends into the interior of the oil reservoir whereupon the hollow tube becomes a housing for the dipstick. Within the oil reservoir, the inboard end of the dipstick becomes immersed within the fluid disposed within the reservoir. The extent of insertion of the dipstick into the reservoir is limited to a constant value established commonly by some form of stop on the dipstick which engages the outboard end of the tube to limit that distance by which the dipstick may be inserted into the reservoir. Such extent of insertion distance is thus maintained constant over each and every time the dipstick is inserted into the reservoir. By this means, upon withdrawal of the dipstick from the reservoir, the level of fluid on that end of the dipstick which is inserted into the reservoir is indicative of the level (quantity) of fluid within the reservoir. Other than during the action of checking the level of fluid within the reservoir, the dipstick is stored within its tubular housing. The structure of the outboard end of the dipstick may include a structural element which is frictionally slidably received within the outboard end of the tubular housing and serves in part to seal off the open outboard end of housing. These devices are prone to leakage of lubricant fluid from the tubular housing and fail to ensure the retention of the dipstick within the housing under certain vehicle operating conditions.
In certain motor vehicles, such as racing cars, the operation of the vehicle may build up inordinate pressure within the oil reservoir. Such pressure levels may be sufficient to “blow out” a prior art dipstick from its elongated tubular housing with obvious disastrous results which may include starting a fire within the engine compartment of the vehicle. Also, there exist the problems associated with oil leaking onto a race trace, resulting in slick tires, crashes and monetary penalties.
Furthermore, a prior art oil reservoir dipstick can become freed from its housing, thereby allowing air to leak through the dipstick housing into the engine crankcase. Certain motor vehicles, such as racing cars of the type typically used in the drag racing industry, are equipped with vacuum systems configured to assist in evacuating the crankcase of the vehicle engine, thereby increasing the overall horsepower of the vehicle during operation. In such vehicles, air leakage into the crankcase interferes with the vacuum system, thereby resulting in decreased horsepower of the vehicle.